Abichites ovalis Korn & Hairapetian, 2021

Korn, Dieter, Hairapetian, Vachik, Ghaderi, Abbas, Leda, Lucyna, Schobben, Martin & Akbari, Amir, 2021, The Changhsingian (Late Permian) ammonoids from Baghuk Mountain (Central Iran), European Journal of Taxonomy 776, pp. 1-106 : 92-93

Abichites ovalis Korn & Hairapetian sp. nov.

urn:lsid:zoobank.org:act:983F405A-033F-49EB-8D75-E5F917F23D86

Fig. 58 ; Table 32

Diagnosis

Species of Abichites with conch reaching 85 mm dm. Subadult stage with subcircular, weakly compressed whorl profile (ww/wh =0.80–1.00) and rounded venter; about 12 shallow and rounded radial ribs. Adult stage with parallel sided or weakly trapezoidal, weakly compressed whorl profile (ww/wh =0.80–1.00), rounded venter and narrowly rounded ventrolateral shoulder; shallow wide ribs on the flank. Prongs of external lobe simple; altogether 7–11 notches of E, A and L lobes.

Etymology

From the Latin ‘ ovalis ’, meaning ‘oval’, because of the oval whorl profile in the subadult stage.

Material examined

Holotype IRAN • Esfahan Province, Baghuk Mountain B section ; Hambast Formation; illustrated in Fig. 58A ; MB.C.30059 .

Paratypes IRAN • 1 specimen; Esfahan Province, Baghuk Mountain B section ; Hambast Formation; MB.C.30060 • 3 specimens; Esfahan Province, Baghuk Mountain C section ; Hambast Formation; MB.C.30061 to MB.C.30063 • 6 specimens; Esfahan Province, Baghuk Mountain E section ; Hambast Formation; MB.C.30064 to MB.C.30069 • 2 specimens; Esfahan Province, Baghuk Mountain G section ; Hambast Formation; MB.C.30070 to MB.C.30071 • 1 specimen; Esfahan Province, Baghuk Mountain H section ; Hambast Formation; MB.C.30072 .

Description

Holotype MB.C.30059 is a rather well-preserved specimen with 62 mm conch diameter; the phragmocone diameter is 44 mm and 190 degrees of the body chamber are preserved ( Fig. 58A ). The adult whorl profile is weakly trapezoidal with gently diverging, slightly concave flanks, a rounded ventrolateral shoulder and a slightly flattened but broadly rounded venter. One volution earlier, the whorl profile is subcircular and weakly compressed (ww/wh = 0.90). The sculpture on the phragmocone consists of 12 shallow and rounded radial ribs per volution. They become weaker on the body chamber but develop to elongate, rather sharp nodes on the outer flank.

The suture line of holotype MB.C.30059 shows an external lobe with flanks standing parallel in the lower part and diverging in the upper part. The prongs are very narrow, lanceolate and not secondarily serrated. On the outer flank lies the symmetric adventive lobe with semicircular, strongly serrated base; it is followed by a rather high lateral saddle and a parallel-sided lateral lobe with five small notches ( Fig. 58C ).

Paratype MB.C.30071 has 60 mm conch diameter and is, with its weakly trapezoidal whorl profile and the general conch shape very similar to the previous one but has a more slender conch (ww/wh =0.85). It shows, in the inner whorls, weak ventrolateral nodes connected to the shallow radial ribs ( Fig. 58B ).

Remarks

Abichites ovalis sp. nov. closely resembles A. paucinodum , but differs in the whorl profile (diverging flanks in A. ovalis sp. nov. but converging in A. paucinodum ), the wider umbilicus in A. ovalis sp. nov. and in the rounded venter in A. ovalis sp. nov. (flat in A. paucinodum ).

Stratigraphic range

Upper part of the Hambast Formation; 0.75 to 0.40 m below the extinction horizon ( Abichites stoyanowi Zone to lowest part of the Arasella minuta Zone ).

Figures

Fig. 58. Abichites ovalis Korn & Hairapetian sp. nov. A. Lateral and dorsal view, holotype MB.C.30059, section B, float. B. Lateral and dorsal view, paratype MB.C.30071, section G, -0.40 m. C. Suture line, holotype MB.C.30059, at 14.2 mm wh. D. Whorl profile proportions. Abbreviation: see Material and methods. Scale bar units= 1 mm.